1. Field of the Invention
The present invention relates to a lead frame applicable to a resin-encapsulated optical module, an optical module employing this lead module, and a method of making the optical module.
2. Related Background Art
Researches and developments are being made in optical modules in which an optical fiber, a ferrule, and a semiconductor optical device are mounted on a substrate, bonded onto a lead frame, and then resin-encapsulated by transfer molding. There have been no reports in conferences or the like concerning a mass production method in which a highly reliable optical module can be made.
Such an optical module comprises an optical fiber, a ferrule, a semiconductor laser diode, a substrate, and a resin body. The substrate is formed with an optical fiber support groove for supporting the optical fiber, and a ferrule support groove for supporting the ferrule. On the substrate, the optical fiber is provided in the optical fiber support groove, the ferrule is provided in the ferrule support groove, and the semiconductor laser diode is provided so as to be optically coupled to the optical fiber. After this substrate is bonded on the lead frame, wire bondings are made. After the resulting assembly is subsequently resin-encapsulated, the lead frame is cut, and the leads are bent. As a result, the finished optical module is provided.
FIG. 1 is a plan view of a lead frame that can be applied to such an optical module. The lead frame 90 comprises an island 93 and support portions 94. The above-mentioned substrate is mounted on the island 93. Each support portion 94 connects the island 93 to either a frame 91 or a tie bar 92, thereby supporting the island 93. The support portions 94 extend from three sides of the island 93 in the respective directions perpendicular to their corresponding sides, thereby reaching either the frame 91 or tie bars 92.
In a method of making the optical module, an optical module principal portion mounted with the ferrule is bonded to the island. For resin encapsulating the optical module principal portion and the lead frame, the lead frame mounted with the optical module principal portion is placed in an encapsulating die so as to be resin-encapsulated.
Having studied this optical module, the inventor has found the following points.
Since the island is supported by the support portions extending along three respective directions, the island does not have a sufficient flexibility with respect to the outer frame of the lead frame. When the lead frame is placed in the encapsulating die, care must be taken so that no force is applied from the encapsulating die to the ferrule mounted on the optical module principal portion.: It is necessary that the lead frame is placed in the encapsulating die after the optical module principal portion is correctly aligned with the lead frame and then bonded to it. Otherwise, it is necessary that the optical module principal portion is correctly aligned with the lead frame on the encapsulating die. This procedure needs much time for aligning the optical module principal portion.
It is an object of the present invention to provide a lead frame which can reduce the force applied to the ferrule from an encapsulating die, an optical module made with this lead frame, and a method of making this optical module.
The lead frame in accordance with the present invention is utilized for mounting an optical module principal portion. The optical module principal portion includes an optical module substrate. Placed on the substrates are an optical fiber, a ferrule, and a semiconductor optical device optically coupled to the optical fiber. The lead frame comprises an island portion, a frame portion, and an island support portion. The island portion is provided so as to mount the optical module principal portion such that the ferrule aligns with a predetermined axis. The frame portion is provided so as to support the island portion. The island support portion is provided so as to connect the island portion and the frame portion to each other, and has a plurality of bent portions. The island support portion extends from the island portion and bends at a plurality of positions, so as to reach the frame portion. As a consequence, when the optical module principal portion is resin-encapsulated using an encapsulating die, the misalignment between the ferrule mounted on the substrate and the encapsulating die can be reduced by the island support portion.
The lead frame in accordance with the present invention can further comprise a substrate support portion provided so as to support the optical module principal portion mounted on the island portion. The substrate support portion is separated from the island portion. The island portion has a notch, whereas the end of the substrate support portion is positioned within the notch. Also, the lead frame in accordance with the present invention can comprise a pair of substrate support portions. The pair of substrate support portions can be arranged such that the predetermined axis is provided between the pair of substrate support portions.
Various kinds of arrangements can be applied to the island support portion of the lead frame in accordance with the present invention as follows. The island support portion can comprise a first part extending from the island portion in a direction intersecting the predetermined axis, a second part extending from the first part along the predetermined axis, and a third part extending from the second part in a direction intersecting the predetermined axis. Alternatively, the island support portion can comprise a fourth part extending from the island portion along the predetermined axis, a fifth part extending from the fourth part in a direction intersecting the predetermined axis, and a sixth part extending from the fifth part along the predetermined axis. The island support portion can include a part thinner than the island portion.